T2 Conception and Development

• What is gametogenesis?

  The process of forming gametes (sperm and eggs) through meiosis.
• What is the average amount of eggs a female will make throughout her lifetime?

  About 400 - 500 eggs.
• What is conception?

  Fertilization.
• How long is an ovum considered fertile?

  24 hours.
• How long can sperm survive in the woman's body?

  3 days.
• Where does fertilization occur in the body?

  Outer third of the fallopian tube.
• How long does it take a zygote to go down the remainder of the fallopian tube?

  3 - 4 days.
• How long does it take implantation to occur?

  6 - 10 days after fertilization.
• When is the embryonic stage for fetal development?

  Day 15 up to week 8.
• When is the fetal stage of development?

  Week 8 to birth.
• When does the embryo start to look more human?

  Around 8 weeks.
• When does the primary germ layer form?

  3 weeks after conception.
• What is formed with the primary germ layers?

  Ectoderm, mesoderm, endoderm.
• What is the most critical time of development?

  The embryonic stage.
• During the 1st trimester, where is amniotic fluid derived from?

  Mother's blood supply.
• During the 2nd and 3rd trimesters, where are some of the fluid sources derived from?

  Fetal sources.
• At term, about how much amniotic fluid is there?

  700 - 800 mL.
• What does amniotic fluid do?

  Antibacterial properties, provides a cushion to protect the child from injury.
• What does the yolk sac do?

  Transfers maternal nutrients and oxygen to the embryo.
• What connects and circulates blood and nutrients through the embryo, connecting stalk, chorion, and yolk sac by the end of week 3?

  Primitive heart.
• When does the yolk sac degenerate?

  By week 5 - 6.
• By the 14th day, embryonic structures are connected to the chorionic villi by what?

  A connecting stalk that grows into the umbilical cord.
• At term, how long is the umbilical cord usually?

  40 - 70 cm in length with a spiral appearance.
• What covers the blood vessels of the umbilical cord to protect from compression and occlusion?

  Wharton's jelly.
• When does the placenta formation start?

  At implantation.
• What are cotyledons?

  Sections of chorionic villi in the placenta.
• About how many cotyledons are made once the placenta is fully developed?

  15 - 20.
• When are circulation and transfer of nutrients in place?

  17 days after conception.
• When does permeability increase?

  By the 5th month.
• When is the structure of the placenta complete?

  12 weeks.
• When does the placenta stop widening?

  20 weeks.
• What are the three main functions of the placenta?

  Endocrine function, metabolic function, and circulatory function.
• What is hormone secreted by the placenta that can be detected in maternal serum?

  hCG (human chorionic gonadotropin).
• When can hCG be detected?

  8 - 10 days after conception.
• What other hormone aside from hCG is secreted by the placenta?

  Progesterone.
• What produces progesterone before the placenta?

  Corpus luteum.
• When does the corpus luteum regress?

  Around 9 weeks.
• When does the placenta produce estrogen?

  Week 7.
• What metabolic functions does the placenta perform?

  Respiration, nutrition, excretion, and storage.
• What has the greatest effect on placental perfusion?

  Maternal blood pressure.